Thread for retaining ring on old Compur shutter?

[HMNB32]

I recently came into a C.P. Goerz Berlin 240mm f6.8 Dagor in an old Compur dial set shutter.

The shutter has the serial number 709672, and the lens 295059.

I want to design and 3D print a lens board that I can just screw the lens into, but I don't know what thread a retaining ring
would have, which would be the same thread I would design into the lens board.

I haven't been able to find anything online, so if anyone knows what the thread would be or has a link to somewhere I could probably find it
I'd greatly appreciate it.

[Louis Pacilla]

I believe this could be what your after. http://skgrimes.com/library/used-obsolete-discontinued-shutters/compur

I do see yours is an older dial set Compur but they may share the same size mounting threads so a #1 rim = #1 dial or #2 rim = #2 dial? If you have the shutter in hand and few simple measuring tools you should be able to find the numbers yourself if no one pops up with a direct response.

[Keith Pitman]

The 0, 1, and 3 are the same as Copals. If you have a Copal, use its ring to test.

[Jim Jones]

If you thread the shutter directly into the lens board, you may have to shim the shutter until it is correctly orientated on the board.

[David Lindquist]

This may be the SK Grimes information Louis wanted to convey: http://skgrimes.com/products/mounting-flanges/metric-stock-flanges

At first I was afraid their website no longer had this. From "Home", click on "Products" which leads you to mounting flanges and retaining rings. There you have a choice of metric or USA. Metric gives you the diameter and thread pitch of the the mounting thread for a number of shutters including the old dial-set Compurs. As you will see these are all described as having a pitch of 0.9mm. The USA section gives the equivalent information for shutters made by Wollensak and Ilex.

Personally I consider their prices for the stock flanges and retaining rings for these old shutters to be very reasonable. You might consider buying one to use with your 3D printed board. This would take care of the consideration raised by Jim Jones.

David

[Leigh]

0,9mm is not a standard metric thread pitch.

However, it is very close to the standard US/English 28TPI (Threads-per-Inch).
Most likely the metric value is actually an approximation of the English pitch.

This was a known technique for European manufacturers to prevent competitors from making compatible products. For example, Leica used English threads on its camera lenses and microscope objectives.

It's quite easy for an American or convertible English/Metric lathe to cut such threads, but difficult or impossible to do it with a Metric-only lathe.

- Leigh